The present invention relates to chain saw guide bars and in particular to an arrangement for mounting a guide bar to a chain saw housing.
Chain saw guide bars are normally attached to the machine unit of a chain saw by two threaded bolts penetrating a longitudinal slot at the rear end of the guide bar, allowing a longitudinal displacement of the guide bar which is needed when replacing a saw chain or compensating for wear of the chain.
Commonly, the guide bar is symmetric with the slot along a longitudinal center line of the guide bar, making it possible to turn the guide bar over to wear both sides of the bar equally. Behind the guide bar is a drive shaft with a drive sprocket for the chain. The bolts are often located to cause the bar center line to pass through the drive shaft, as disclosed in U.S. Pat. No. 3,683,980 and U.S. Pat. No. 3,955,279, but it is also known to cause the center line to pass below the shaft as disclosed in U.S. Pat. No. 2,845,967, U.S. Pat. No. 2,910,100 and U.S. Pat. No. 3,059,491 to allow a larger deflection of the slack upper part of the chain. With the introduction of self-tensioning drive sprockets as shown in DE 41 37 409 or SE 469 515 it has also been suggested to cause the bar centerline to pass above the drive shaft.